Dear agony stricken boy,
I am sorry to hear about your state. Firstly panicking about what ifs about grades and exams will never help, if anything, it will add more pressure to your already existing worries.So firstly, take a deep breath and relax. Now coming to getting straight A*'s , you seem to have worked hard throughout the year and now you are giving into the pressure your mind is feeling, my advice, look at it from this perspective, you are almost there and you know with a little more hard work and concentration, you will get what you want. Second point arises from the first..its the want to excel...you have so far seem to have done excellently, so you pretty much have it embedded in your sub-concious mind to want to be the best, dont let that die down..that motivation should help you look at newer challenges with a perspective of proving yourself. However, I will advice you against a "all work and no play" regime. That never works out..because at the end, you are totally exhausted with no relaxation..try the following to ease your pressure:
Set up a time table for study for your different courses.
Set an hour or twos break per half day of study..in that one - two hour, play games, watch TV, read novels or just chill out, without thinking about studies..how tht helps is, you will start to realise you need to get back to studying..and that urge will take you back to studying for the next couple of hours..so, take breaks in your study hours...no one can get soo busy to not find an hours gap in the whole day...you have to make a routine for yourself and follow it till you have finished your exams etc.
Talking to parents and teachers wouldnt help for a single reason, that they have been there, done that, and they think, as they got over it and faired well, so will you..so there is really no point on that.
As for being called the geek, ignore such comments, because at the end of the day, you know will fair well in he exams and all tht matters is tht your grades / scores will determine where you go next and for a better and brighter future you will need good scores , so ignore their comments as ignorance...since by the time they realise that the time they spent commeting on you, you studied and they wasted and in the end, you scored higher than them..so just cast a deaf ear on them...and your true friends wil never laugh at you, but will help you and try to become like you...
One more thing..take things one at a time, concentrate on the immediate exams or challenges..dont worry about things an year from now. Take step by step actions and finish things one at a time...so that when you are the end of it, you have only that last thing to get over with.
Last but not the least, the world is a very competitive place, you have to have the edge to fight it out and you will develop that only by working hard and not giving into pressure..also a certain amount of nervousness and tension is good , that will make you thorough about all that you study and learn...
Good Luck and relax
-Agony Aunt Sunaina.